. >> reporter: we partnered with a science and his students to find what was lurking in local bags. >> we just wipe round the areas where kids are most likely to touch. the handle and the top but also a bit of the front and the back. >> reporter: they swabbed more than 100 bags provided by three elementary schools. then went back to the lab to transfer cells from the swabs to dishes. >> you can see a variety of different things on any one box. >> reporter: what grew may gross you out. 59 of the 103 bags had low levels of staph, two had high amounts. >> having something like this get in to the wrong place at the wrong time could lead to a potential infection. >> reporter: including mrsa. the low levels of yeast are okay but that could mean the bags have big problems. >> they indicate just the fact that my box is coming in contact with vegetation, my food or sitting it on the lawn as i wait for the bus. >> reporter: and he found something that is very bad, 23 bags had fecal bacteria, four had dangerously high levels. >> get in to the system and in a good sized dose can cause you gastric